diff --git a/compact.go b/compact.go
index f5a2045eb..dd7bc3832 100644
--- a/compact.go
+++ b/compact.go
@@ -67,9 +67,12 @@ type LeveledCompactor struct {
 }
 
 type compactorMetrics struct {
-	ran      prometheus.Counter
-	failed   prometheus.Counter
-	duration prometheus.Histogram
+	ran          prometheus.Counter
+	failed       prometheus.Counter
+	duration     prometheus.Histogram
+	chunkSize    prometheus.Histogram
+	chunkSamples prometheus.Histogram
+	chunkRange   prometheus.Histogram
 }
 
 func newCompactorMetrics(r prometheus.Registerer) *compactorMetrics {
@@ -83,9 +86,25 @@ func newCompactorMetrics(r prometheus.Registerer) *compactorMetrics {
 		Name: "tsdb_compactions_failed_total",
 		Help: "Total number of compactions that failed for the partition.",
 	})
-	m.duration = prometheus.NewSummary(prometheus.SummaryOpts{
-		Name: "tsdb_compaction_duration",
-		Help: "Duration of compaction runs.",
+	m.duration = prometheus.NewHistogram(prometheus.HistogramOpts{
+		Name:    "tsdb_compaction_duration",
+		Help:    "Duration of compaction runs.",
+		Buckets: prometheus.ExponentialBuckets(1, 2, 10),
+	})
+	m.chunkSize = prometheus.NewHistogram(prometheus.HistogramOpts{
+		Name:    "tsdb_compaction_chunk_size",
+		Help:    "Final size of chunks on their first compaction",
+		Buckets: prometheus.ExponentialBuckets(32, 1.5, 12),
+	})
+	m.chunkSamples = prometheus.NewHistogram(prometheus.HistogramOpts{
+		Name:    "tsdb_compaction_chunk_samples",
+		Help:    "Final number of samples on their first compaction",
+		Buckets: prometheus.ExponentialBuckets(4, 1.5, 12),
+	})
+	m.chunkRange = prometheus.NewHistogram(prometheus.HistogramOpts{
+		Name:    "tsdb_compaction_chunk_range",
+		Help:    "Final time range of chunks on their first compaction",
+		Buckets: prometheus.ExponentialBuckets(100, 4, 10),
 	})
 
 	if r != nil {
@@ -93,6 +112,9 @@ func newCompactorMetrics(r prometheus.Registerer) *compactorMetrics {
 			m.ran,
 			m.failed,
 			m.duration,
+			m.chunkRange,
+			m.chunkSamples,
+			m.chunkSize,
 		)
 	}
 	return m
@@ -312,6 +334,25 @@ func (c *LeveledCompactor) Write(dest string, b BlockReader, mint, maxt int64) e
 	return c.write(dest, meta, b)
 }
 
+// instrumentedChunkWriter is used for level 1 compactions to record statistics
+// about compacted chunks.
+type instrumentedChunkWriter struct {
+	ChunkWriter
+
+	size    prometheus.Histogram
+	samples prometheus.Histogram
+	trange  prometheus.Histogram
+}
+
+func (w *instrumentedChunkWriter) WriteChunks(chunks ...ChunkMeta) error {
+	for _, c := range chunks {
+		w.size.Observe(float64(len(c.Chunk.Bytes())))
+		w.samples.Observe(float64(c.Chunk.NumSamples()))
+		w.trange.Observe(float64(c.MaxTime - c.MinTime))
+	}
+	return w.ChunkWriter.WriteChunks(chunks...)
+}
+
 // write creates a new block that is the union of the provided blocks into dir.
 // It cleans up all files of the old blocks after completing successfully.
 func (c *LeveledCompactor) write(dest string, meta *BlockMeta, blocks ...BlockReader) (err error) {
@@ -338,10 +379,22 @@ func (c *LeveledCompactor) write(dest string, meta *BlockMeta, blocks ...BlockRe
 
 	// Populate chunk and index files into temporary directory with
 	// data of all blocks.
-	chunkw, err := newChunkWriter(chunkDir(tmp))
+	var chunkw ChunkWriter
+
+	chunkw, err = newChunkWriter(chunkDir(tmp))
 	if err != nil {
 		return errors.Wrap(err, "open chunk writer")
 	}
+	// Record written chunk sizes on level 1 compactions.
+	if meta.Compaction.Level == 1 {
+		chunkw = &instrumentedChunkWriter{
+			ChunkWriter: chunkw,
+			size:        c.metrics.chunkSize,
+			samples:     c.metrics.chunkSamples,
+			trange:      c.metrics.chunkRange,
+		}
+	}
+
 	indexw, err := newIndexWriter(tmp)
 	if err != nil {
 		return errors.Wrap(err, "open index writer")